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    <meta name="description" content="题目描述判断一个整数是否是回文数。回文数是指正序（从左向右）和倒序（从右向左）读都是一样的整数。 示例:1234567891011#1输入: 121输出: true#2输入: -121输出: false解释: 从左向右读, 为 -121 。 从右向左读, 为 121- 。因此它不是一个回文数。#3输入: 10输出: false解释: 从右向左读, 为 01 。因此它不是一个回文数。  思路 最好理">
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            <h1 style="display: none">每日一题——回文数</h1>
            
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              <h1 id="题目描述"><a href="#题目描述" class="headerlink" title="题目描述"></a>题目描述</h1><p>判断一个整数是否是回文数。回文数是指正序（从左向右）和倒序（从右向左）读都是一样的整数。</p>
<h3 id="示例"><a href="#示例" class="headerlink" title="示例:"></a>示例:</h3><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><code class="hljs bash"><span class="hljs-comment">#1</span><br>输入: 121<br>输出: <span class="hljs-literal">true</span><br><span class="hljs-comment">#2</span><br>输入: -121<br>输出: <span class="hljs-literal">false</span><br>解释: 从左向右读, 为 -121 。 从右向左读, 为 121- 。因此它不是一个回文数。<br><span class="hljs-comment">#3</span><br>输入: 10<br>输出: <span class="hljs-literal">false</span><br>解释: 从右向左读, 为 01 。因此它不是一个回文数。<br></code></pre></td></tr></table></figure>

<h1 id="思路"><a href="#思路" class="headerlink" title="思路"></a>思路</h1><ul>
<li>最好理解的一种解法就是先将 <strong>整数转为字符串</strong> ，然后将字符串分割为数组，只需要循环数组的一半长度进行判断对应元素是否相等即可。    </li>
<li>类似前面的整数反转，将反转之后的数字与之前的作比较。</li>
</ul>
<h1 id="代码"><a href="#代码" class="headerlink" title="代码"></a>代码</h1><h3 id="PHP"><a href="#PHP" class="headerlink" title="PHP"></a>PHP</h3><figure class="highlight php"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><code class="hljs php"><span class="hljs-comment">/**</span><br><span class="hljs-comment"> * <span class="hljs-doctag">@param</span> Integer $x</span><br><span class="hljs-comment"> * <span class="hljs-doctag">@return</span> Boolean</span><br><span class="hljs-comment"> */</span><br><span class="hljs-comment"># 方法一</span><br><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">isPalindrome</span>(<span class="hljs-params"><span class="hljs-variable">$x</span></span>) </span>&#123;<br>    <span class="hljs-keyword">return</span> strrev(<span class="hljs-variable">$x</span>) == <span class="hljs-variable">$x</span>;	<span class="hljs-comment">// 字符串反转</span><br>&#125;<br><span class="hljs-comment"># 方法二</span><br><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">isPalindrome</span>(<span class="hljs-params"><span class="hljs-variable">$x</span></span>) </span>&#123;<br>    <span class="hljs-variable">$n</span> = <span class="hljs-variable">$x</span>;       <br>    <span class="hljs-variable">$reverse</span> = <span class="hljs-number">0</span>;<br>    <span class="hljs-keyword">while</span> (<span class="hljs-variable">$n</span> &gt; <span class="hljs-number">0</span>) &#123;<br>        <span class="hljs-variable">$reverse</span> = <span class="hljs-variable">$reverse</span> * <span class="hljs-number">10</span>;<br>        <span class="hljs-variable">$reverse</span> = <span class="hljs-variable">$reverse</span> + <span class="hljs-variable">$n</span> % <span class="hljs-number">10</span>;	<span class="hljs-comment">// 整数反转</span><br>        <span class="hljs-variable">$n</span> = (<span class="hljs-keyword">int</span>)(<span class="hljs-variable">$n</span>/<span class="hljs-number">10</span>);<br>    &#125;<br><br>    <span class="hljs-keyword">return</span> <span class="hljs-variable">$x</span> === <span class="hljs-variable">$reverse</span>;<br>&#125;<br></code></pre></td></tr></table></figure>

<h3 id="Golang"><a href="#Golang" class="headerlink" title="Golang"></a>Golang</h3><figure class="highlight go"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br></pre></td><td class="code"><pre><code class="hljs go"><span class="hljs-comment">// 方法一：整数转为字符串后前后比较</span><br><span class="hljs-function"><span class="hljs-keyword">func</span> <span class="hljs-title">isPalindrome</span><span class="hljs-params">(x <span class="hljs-keyword">int</span>)</span> <span class="hljs-title">bool</span></span> &#123;<br>    <span class="hljs-keyword">if</span> x &lt; <span class="hljs-number">0</span> &#123;<br>        <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span><br>    &#125;<br><br>    <span class="hljs-keyword">var</span> str = strconv.Itoa(x)<br>    <span class="hljs-keyword">for</span> i := <span class="hljs-keyword">range</span> str&#123;<br>        <span class="hljs-keyword">if</span> str[<span class="hljs-built_in">len</span>(str)<span class="hljs-number">-1</span>-i] != str[i] &#123;<br>            <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span><br>        &#125;<br>    &#125;<br>    <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span><br>&#125;<br><br><span class="hljs-comment">// 方法二：整数反转与原始数字比较</span><br><span class="hljs-function"><span class="hljs-keyword">func</span> <span class="hljs-title">isPalindrome</span><span class="hljs-params">(x <span class="hljs-keyword">int</span>)</span> <span class="hljs-title">bool</span></span> &#123;<br>    <span class="hljs-comment">// 负数肯定不是回文</span><br>    <span class="hljs-keyword">if</span> x &lt; <span class="hljs-number">0</span> &#123;<br>        <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span><br>    &#125;<br>    <span class="hljs-comment">// 记录下原始数字</span><br>    originX := x  <br>    <span class="hljs-comment">// 反转数字</span><br>    rev := <span class="hljs-number">0</span><br>    <span class="hljs-keyword">for</span> x != <span class="hljs-number">0</span> &#123;<br>        pop := x % <span class="hljs-number">10</span><br>        x /= <span class="hljs-number">10</span><br>        rev = rev * <span class="hljs-number">10</span> + pop<br>    &#125;   <br>    <span class="hljs-comment">// 原始数字和反转数字对比</span><br>    <span class="hljs-keyword">return</span> originX == rev<br>&#125;<br></code></pre></td></tr></table></figure>


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